There is no mystery about Michael Clarke. The elegant Australian No 5 scored a couple of hundreds against England in the bad old days of 2006-07 and has added a couple more this summer, plus a 93 yesterday. But who is this Marcus North who has partnered Clarke in fifth-wicket stands of 149 in Cardiff, 185 at Edgbaston and 152 here yesterday?

In the space of a week this odd couple have been the principals in saving one Test and propelled Australia into a comfort zone from which they have become favourites to retain the Ashes.

For North, this is a remarkable story. Nearing 30, he must have had few illusions about a late flourish in his career but he wasn't to know that Andrew Symonds would implode in a blur of drink and insubordination. North saw his opportunity at No 6 and he took it: two hundreds in South Africa last winter; two more in this Ashes series, 125 not out at Cardiff, 110 in Leeds before he holed out just short of cow corner – not to mention his 96 in Birmingham. Only Lord's (a duck and six) has proved a disappointment.

North, who has just reached 30, is not far short of six foot with a bland expression – a more solid figure than Clarke, who is two years younger. He is a slow starter, accumulating only seven off 42 balls on Friday evening (discipline comes from playing on quick wickets in Perth, he says) when staying at the crease was a priority. Consequently, the strongest image of his batting is of stern defence and well-judged leaves.

But as his score began to build yesterday, he hit into the V and towards the end of the innings he became slightly skittish, moving outside his off stump to hit the ball into space on the leg side. On 96, when he noticed Andrew Strauss bringing in the field to stop a run, he heaved Graeme Swann's delivery to square leg, not waiting for the ball to clear the boundary before turning to the pavilion and leaping high, arms outstretched.

It was, he said, probably the best single moment in his career, in what had been – until this year – an unspectacular life in domestic Australian and English cricket.

What Clarke and North have in common is the top places in Australia's healthy batting averages in the series so far. Clarke is No 1 with 89.00; North comes second with 69.80. What a comfort these figures bring to a captain who was uncertain about his top order.

Otherwise, it would be difficult to conceive two more different career paths. Clarke is 28, though he is still know as "Pup", because that is what he was called when he was a pup, making his one-day debut in January 2003.

The only serious setback in Clarke's life in cricket was after the 2005 Ashes series when Simon Jones found him out and he was told to return to domestic cricket and reacquaint himself with the basics. He did so with a vengeance and by this summer his Test average had floated over 50, he had been promoted to vice-captain and is widely expected to succeed Ricky Ponting.

He has a glamorous girlfriend, the delightfully named Laura Bingle, who is a model. He learned the dubious art of celebrity directly from Shane Warne.

Before this Test began, the greatest concern was whether the behaviour of the inhabitants of the West Stand would prove intolerable. Security guards privately refer to the stand as "Basra". But expectations were wrong. One reason for this is that the dominance of Clarke and North gave them nothing to cheer about, or to jeer at. They are a powerful presence.